Mycobacteria in soil and their relation to disease-associated strains.

Abstract

It has been known for a long time that large numbers of rapidly growing mycobacteria may be found in the soil (1, 2), but relatively few attempts have been made to study the total mycobacterial flora by comprehensive techniques. The ability of the soil to harbor mycobacteria has assumed greater significance recently because of the possibility that disease caused by mycobacteria other than mammalian tubercle bacilli may arise by contamination of humans from a common source in the environment. The lack of person-to-person communicability, the evidence of widespread infection early in life afforded by the results of skin test surveys, and geographic differences in the rates of infection and disease caused by various groups of the atypical mycobacteria are some of the facts that point to the soil as the reservoir from which human infection might occur. Schalk and his co-workers (3) in 1935 showed that soil contaminated with avian tubercle bacilli remained infectious for fowl and swine for at least four years. Several recent studies demonstrated that certain varieties of potentially pathogenic mycobacteria can be found in the soil; Singer and Rodda ( 4, 5), Kubica and co-workers (6), Jeffries and associates (7), and Jones and Jenkins (8) reported the isolation of rapidly growing mycobacteria, scotochromogenic mycobacteria, and Group III, or nonchromogenic acid-fast bacilli. Strains of Mycobacterium kansasii, however, have not as yet been identified in the soil. The present report summarizes the results of cultures for mycobacteria of 72 soil specimens